The present invention relates to a fuel tank, particularly a tank for storing and transferring a fuel as a carrier for hydrogen.
Hydrogen is considered to be an auspicious energy source of substitute for petroleum oil under an increase in importance of global warming or energy security. On the other hand, there is a problem of that hydrogen is gaseous matter under normal temperature and normal pressure and is easily ignited. Therefore, a development of method for safely storing hydrogen if high density and a development of system for supplying and utilizing hydrogen are needed.
As a device for utilizing hydrogen as fuel, a fuel cell attracts attention. Hydrogen is used as fuel in the fuel cell, but it is difficult for hydrogen as fuel to be safely and stably supplied. A fuel cell for an automobile needs to be of small size and of light weight, of a long cruising distance per one fuel-charge, of easy handling on charging, or the like, and various supply methods for these requirements are proposed.
For examples as methods for storing and supplying hydrogen, hydrogen is directly supplied from compressed hydrogen or liquefied hydrogen, supplied from a hydrogen absorbing member such as hydrogen absorbing alloy, carbon nano-tube or the like, or is generated by reforming a methanol, hydrocarbon or the like as hydrogen compound storing hydrogen. As the method of directly supplying hydrogen from the compressed hydrogen, a fuel cell automobile of compressed hydrogen type can be now realized by a development of weight-saving and pressure-proof of high pressure hydrogen gas container, but there is a problem in safety to be kept during and after charging while increasing a compression ratio of hydrogen to increase the cruising distance. Therefore, a safety technique for preventing hydrogen from exploding and restraining temperature from increasing is developed. The method of reforming hydrocarbon to generate hydrogen attracts attention, because it is useable during a long term while keeping the conventional sources on a transition from petroleum fuel to hydrogen fuel. However, high temperature necessary for the reforming causes radical reaction, so the reforming is utilized only experimentally.
On the other hand, as a substitute for the above methods, inorganic or organic hydride as hydrogen storing material of high hydrogen absorbing performance attracts attention in recent years. The hydrogen storing material is of liquid under normal temperature, and has the same physical properties as the gasoline so that the conventional infrastructure for the petroleum fuel is partially useable. Further, an explosibility thereof is relatively lower than the other hydrogen fuel, so it is effective for decreasing the cost and increasing the safety for supplying. As a feature of the hydrogen storing material, a compound as dehydrogenation product as well as hydrogen are generated on the dehydrogenation reaction. The compound as dehydrogenation product is repeatedly useable to be mixed with hydrogen and to be removed from hydrogen so that the cost for supplying the hydrogen storing material can be decreased. However, an infrastructure for reusing the compound as dehydrogenation product in the conventional fuel hydrogen utilizing device does not exist. Therefore, a user of the hydrogen storing material must correct the compound as dehydrogenation product. There is a problem for decreasing the size and the space of a tank for correcting the compound as dehydrogenation product. JP-A-2004-250059 discloses a partitioned tank for solving the above problem.